/*
 * Created on 31-Jul-2004
 * Created by Paul Gardner
 * Copyright (C) Azureus Software, Inc, All Rights Reserved.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
 *
 */

package org.gudy.azureus2.core3.disk.impl.access.impl;

import java.util.ArrayList;
import java.util.HashSet;
import java.util.Iterator;
import java.util.List;
import java.util.Set;

import org.gudy.azureus2.core3.disk.DiskManagerReadRequest;
import org.gudy.azureus2.core3.disk.DiskManagerReadRequestListener;
import org.gudy.azureus2.core3.disk.impl.DiskManagerHelper;
import org.gudy.azureus2.core3.disk.impl.access.DMReader;
import org.gudy.azureus2.core3.disk.impl.piecemapper.DMPieceList;
import org.gudy.azureus2.core3.disk.impl.piecemapper.DMPieceMapEntry;
import org.gudy.azureus2.core3.logging.LogEvent;
import org.gudy.azureus2.core3.logging.LogIDs;
import org.gudy.azureus2.core3.logging.Logger;
import org.gudy.azureus2.core3.util.AEMonitor;
import org.gudy.azureus2.core3.util.AESemaphore;
import org.gudy.azureus2.core3.util.Debug;
import org.gudy.azureus2.core3.util.DirectByteBuffer;
import org.gudy.azureus2.core3.util.DirectByteBufferPool;
import org.gudy.azureus2.core3.util.SystemTime;

import com.aelitis.azureus.core.diskmanager.access.DiskAccessController;
import com.aelitis.azureus.core.diskmanager.access.DiskAccessRequest;
import com.aelitis.azureus.core.diskmanager.access.DiskAccessRequestListener;
import com.aelitis.azureus.core.diskmanager.cache.CacheFile;

/**
 * @author parg
 * 
 */
public class DMReaderImpl implements DMReader {
    private static final LogIDs LOGID = LogIDs.DISK;

    private DiskManagerHelper disk_manager;
    private DiskAccessController disk_access;

    private int async_reads;
    private Set read_requests = new HashSet();
    private AESemaphore async_read_sem = new AESemaphore("DMReader:asyncReads");

    private boolean started;
    private boolean stopped;

    private long total_read_ops;
    private long total_read_bytes;

    protected AEMonitor this_mon = new AEMonitor("DMReader");

    public DMReaderImpl(DiskManagerHelper _disk_manager) {
        disk_manager = _disk_manager;

        disk_access = disk_manager.getDiskAccessController();
    }

    public void start() {
        try {
            this_mon.enter();

            if (started) {

                throw (new RuntimeException("can't start twice"));
            }

            if (stopped) {

                throw (new RuntimeException("already been stopped"));
            }

            started = true;

        } finally {

            this_mon.exit();
        }
    }

    public void stop() {
        int read_wait;

        try {
            this_mon.enter();

            if (stopped || !started) {

                return;
            }

            stopped = true;

            read_wait = async_reads;

        } finally {

            this_mon.exit();
        }

        long log_time = SystemTime.getCurrentTime();

        for (int i = 0; i < read_wait; i++) {

            long now = SystemTime.getCurrentTime();

            if (now < log_time) {

                log_time = now;

            } else {

                if (now - log_time > 1000) {

                    log_time = now;

                    if (Logger.isEnabled()) {

                        Logger.log(new LogEvent(disk_manager, LOGID, "Waiting for reads to complete - " + (read_wait - i) + " remaining"));
                    }
                }
            }

            async_read_sem.reserve();
        }
    }

    public DiskManagerReadRequest createReadRequest(int pieceNumber, int offset, int length) {
        return (new DiskManagerReadRequestImpl(pieceNumber, offset, length));
    }

    public boolean hasOutstandingReadRequestForPiece(int piece_number) {
        try {
            this_mon.enter();

            Iterator it = read_requests.iterator();

            while (it.hasNext()) {

                DiskManagerReadRequest request = (DiskManagerReadRequest) ((Object[]) it.next())[0];

                if (request.getPieceNumber() == piece_number) {

                    return (true);
                }
            }

            return (false);

        } finally {

            this_mon.exit();
        }
    }

    public long[] getStats() {
        return (new long[] { total_read_ops, total_read_bytes });
    }

    // returns null if the read can't be performed

    public DirectByteBuffer readBlock(int pieceNumber, int offset, int length) {
        DiskManagerReadRequest request = createReadRequest(pieceNumber, offset, length);

        final AESemaphore sem = new AESemaphore("DMReader:readBlock");

        final DirectByteBuffer[] result = { null };

        readBlock(request, new DiskManagerReadRequestListener() {
            public void readCompleted(DiskManagerReadRequest request, DirectByteBuffer data) {
                result[0] = data;

                sem.release();
            }

            public void readFailed(DiskManagerReadRequest request, Throwable cause) {
                sem.release();
            }

            public int getPriority() {
                return (-1);
            }

            public void requestExecuted(long bytes) {
            }
        });

        sem.reserve();

        return (result[0]);
    }

    public void readBlock(final DiskManagerReadRequest request, final DiskManagerReadRequestListener _listener) {
        request.requestStarts();

        final DiskManagerReadRequestListener listener = new DiskManagerReadRequestListener() {
            public void readCompleted(DiskManagerReadRequest request, DirectByteBuffer data) {
                request.requestEnds(true);

                _listener.readCompleted(request, data);
            }

            public void readFailed(DiskManagerReadRequest request, Throwable cause) {
                request.requestEnds(false);

                _listener.readFailed(request, cause);
            }

            public int getPriority() {
                return (_listener.getPriority());
            }

            public void requestExecuted(long bytes) {
                _listener.requestExecuted(bytes);
            }
        };

        DirectByteBuffer buffer = null;

        try {
            int length = request.getLength();

            buffer = DirectByteBufferPool.getBuffer(DirectByteBuffer.AL_DM_READ, length);

            if (buffer == null) { // Fix for bug #804874

                Debug.out("DiskManager::readBlock:: ByteBufferPool returned null buffer");

                listener.readFailed(request, new Exception("Out of memory"));

                return;
            }

            int pieceNumber = request.getPieceNumber();
            int offset = request.getOffset();

            DMPieceList pieceList = disk_manager.getPieceList(pieceNumber);

            // temporary fix for bug 784306

            if (pieceList.size() == 0) {

                Debug.out("no pieceList entries for " + pieceNumber);

                listener.readCompleted(request, buffer);

                return;
            }

            long previousFilesLength = 0;

            int currentFile = 0;

            long fileOffset = pieceList.get(0).getOffset();

            while (currentFile < pieceList.size() && pieceList.getCumulativeLengthToPiece(currentFile) < offset) {

                previousFilesLength = pieceList.getCumulativeLengthToPiece(currentFile);

                currentFile++;

                fileOffset = 0;
            }

            // update the offset (we're in the middle of a file)

            fileOffset += offset - previousFilesLength;

            List chunks = new ArrayList();

            int buffer_position = 0;

            while (buffer_position < length && currentFile < pieceList.size()) {

                DMPieceMapEntry map_entry = pieceList.get(currentFile);

                int length_available = map_entry.getLength() - (int) (fileOffset - map_entry.getOffset());

                // explicitly limit the read size to the proper length, rather than relying on the underlying file being correctly-sized
                // see long DMWriterAndCheckerImpl::checkPiece note

                int entry_read_limit = buffer_position + length_available;

                // now bring down to the required read length if this is shorter than this
                // chunk of data

                entry_read_limit = Math.min(length, entry_read_limit);

                // this chunk denotes a read up to buffer offset "entry_read_limit"

                chunks.add(new Object[] { map_entry.getFile().getCacheFile(), new Long(fileOffset), new Integer(entry_read_limit) });

                buffer_position = entry_read_limit;

                currentFile++;

                fileOffset = 0;
            }

            if (chunks.size() == 0) {

                Debug.out("no chunk reads for " + pieceNumber);

                listener.readCompleted(request, buffer);

                return;
            }

            // this is where we go async and need to start counting requests for the sake
            // of shutting down tidily

            // have to wrap the request as we can validly have >1 for same piece/offset/length and
            // the request type itself overrides object equiv based on this...

            final Object[] request_wrapper = { request };

            DiskManagerReadRequestListener l = new DiskManagerReadRequestListener() {
                public void readCompleted(DiskManagerReadRequest request, DirectByteBuffer data) {
                    complete();

                    listener.readCompleted(request, data);
                }

                public void readFailed(DiskManagerReadRequest request, Throwable cause) {
                    complete();

                    listener.readFailed(request, cause);
                }

                public int getPriority() {
                    return (_listener.getPriority());
                }

                public void requestExecuted(long bytes) {
                    _listener.requestExecuted(bytes);
                }

                protected void complete() {
                    try {
                        this_mon.enter();

                        async_reads--;

                        if (!read_requests.remove(request_wrapper)) {

                            Debug.out("request not found");
                        }

                        if (stopped) {

                            async_read_sem.release();
                        }
                    } finally {

                        this_mon.exit();
                    }
                }
            };

            try {
                this_mon.enter();

                if (stopped) {

                    buffer.returnToPool();

                    listener.readFailed(request, new Exception("Disk reader has been stopped"));

                    return;
                }

                async_reads++;

                read_requests.add(request_wrapper);

            } finally {

                this_mon.exit();
            }

            new requestDispatcher(request, l, buffer, chunks);

        } catch (Throwable e) {

            if (buffer != null) {

                buffer.returnToPool();
            }

            disk_manager.setFailed("Disk read error - " + Debug.getNestedExceptionMessage(e));

            Debug.printStackTrace(e);

            listener.readFailed(request, e);
        }
    }

    protected class requestDispatcher implements DiskAccessRequestListener {
        private DiskManagerReadRequest dm_request;
        private DiskManagerReadRequestListener listener;
        private DirectByteBuffer buffer;
        private List chunks;

        private int buffer_length;

        private int chunk_index;
        private int chunk_limit;

        protected requestDispatcher(DiskManagerReadRequest _request, DiskManagerReadRequestListener _listener, DirectByteBuffer _buffer,
                List _chunks) {
            dm_request = _request;
            listener = _listener;
            buffer = _buffer;
            chunks = _chunks;

            /*
             * String str = "Read: " + dm_request.getPieceNumber()+"/"+dm_request.getOffset()+"/"+dm_request.getLength()+":"; for (int
             * i=0;i<chunks.size();i++){ Object[] entry = (Object[])chunks.get(i); String str2 = entry[0] + "/" + entry[1] +"/" + entry[2]; str +=
             * (i==0?"":",") + str2; } System.out.println( str );
             */

            buffer_length = buffer.limit(DirectByteBuffer.SS_DR);

            dispatch();
        }

        protected void dispatch() {
            try {
                if (chunk_index == chunks.size()) {

                    buffer.limit(DirectByteBuffer.SS_DR, buffer_length);

                    buffer.position(DirectByteBuffer.SS_DR, 0);

                    listener.readCompleted(dm_request, buffer);

                } else {

                    if (chunk_index == 1 && chunks.size() > 32) {

                        // for large numbers of chunks drop the recursion approach and
                        // do it linearly (but on the async thread)

                        for (int i = 1; i < chunks.size(); i++) {

                            final AESemaphore sem = new AESemaphore("DMR:dispatch:asyncReq");
                            final Throwable[] error = { null };

                            doRequest(new DiskAccessRequestListener() {
                                public void requestComplete(DiskAccessRequest request) {
                                    sem.release();
                                }

                                public void requestCancelled(DiskAccessRequest request) {
                                    Debug.out("shouldn't get here");
                                }

                                public void requestFailed(DiskAccessRequest request, Throwable cause) {
                                    error[0] = cause;

                                    sem.release();
                                }

                                public int getPriority() {
                                    return (listener.getPriority());
                                }

                                public void requestExecuted(long bytes) {
                                    if (bytes > 0) {

                                        total_read_bytes += bytes;
                                        total_read_ops++;
                                    }

                                    listener.requestExecuted(bytes);
                                }
                            });

                            sem.reserve();

                            if (error[0] != null) {

                                throw (error[0]);
                            }
                        }

                        buffer.limit(DirectByteBuffer.SS_DR, buffer_length);

                        buffer.position(DirectByteBuffer.SS_DR, 0);

                        listener.readCompleted(dm_request, buffer);
                    } else {

                        doRequest(this);
                    }
                }
            } catch (Throwable e) {

                failed(e);
            }
        }

        protected void doRequest(DiskAccessRequestListener l) {
            Object[] stuff = (Object[]) chunks.get(chunk_index++);

            if (chunk_index > 0) {

                buffer.position(DirectByteBuffer.SS_DR, chunk_limit);
            }

            chunk_limit = ((Integer) stuff[2]).intValue();

            buffer.limit(DirectByteBuffer.SS_DR, chunk_limit);

            short cache_policy = dm_request.getUseCache() ? CacheFile.CP_READ_CACHE : CacheFile.CP_NONE;

            if (dm_request.getFlush()) {

                cache_policy |= CacheFile.CP_FLUSH;
            }

            disk_access.queueReadRequest((CacheFile) stuff[0], ((Long) stuff[1]).longValue(), buffer, cache_policy, l);
        }

        public void requestComplete(DiskAccessRequest request) {
            dispatch();
        }

        public void requestCancelled(DiskAccessRequest request) {
            // we never cancel so nothing to do here

            Debug.out("shouldn't get here");
        }

        public void requestFailed(DiskAccessRequest request, Throwable cause) {
            failed(cause);
        }

        public int getPriority() {
            return (listener.getPriority());
        }

        public void requestExecuted(long bytes) {
            if (bytes > 0) {

                total_read_bytes += bytes;
                total_read_ops++;
            }

            listener.requestExecuted(bytes);
        }

        protected void failed(Throwable cause) {
            buffer.returnToPool();

            disk_manager.setFailed("Disk read error - " + Debug.getNestedExceptionMessage(cause));

            Debug.printStackTrace(cause);

            listener.readFailed(dm_request, cause);
        }
    }
}
